221720 has 32 divisors (see below), whose sum is σ = 522720. Its totient is φ = 84480.

The previous prime is 221719. The next prime is 221723. The reversal of 221720 is 27122.

221720 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 221695 and 221704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 800 + ... + 1040.

It is an arithmetic number, because the mean of its divisors is an integer number (16335).

2²²¹⁷²⁰ is an apocalyptic number.

221720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (261360).

221720 is an abundant number, since it is smaller than the sum of its proper divisors (301000).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

221720 is a wasteful number, since it uses less digits than its factorization.

221720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275 (or 271 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 14.

The square root of 221720 is about 470.8715323737. The cubic root of 221720 is about 60.5250220929.

Adding to 221720 its reverse (27122), we get a palindrome (248842).

The spelling of 221720 in words is "two hundred twenty-one thousand, seven hundred twenty", and thus it is an iban number.